1. Technical Field
The invention relates generally to an improved cutter bit. More particularly, the invention relates to shaft mounted rotary cutter bits of the type mounted in rotary woodworking machines. Specifically, the invention relates to rotary cutting bits having increased cooling capacity and reduced weight during operation.
2. Background Information
It is customary in building construction, as well as the construction of furniture and cabinetry to impart decorative profiles upon the wood. Moreover, many joints are created by imparting a variety of profiles on the wood to create stronger joints, as well as to provide increased surface areas for glue contact at the joint. Regardless of the reasons of imparting a profile on the wood, the profile may be created in one of two methods. Hand planes may be utilized, which planes have a cutting knife shaped with a negative of the profile to be imparted on the wood. However, such planes are expensive, inaccurate and require significant skill to utilize. As such, many power tools have been specifically designed to impart a desired profile onto a workpiece while existing tools have been modified to allow those tools to also impart the desired profile.
While many such tools exist, routers are by far the most prevalent. Routers include a motor which rotates a chuck at a predetermined or variable speed. When the router operator wishes to impart a given profile onto a workpiece, the shank of a router bit having the desired profile is installed into the chuck. When the motor is activated, the router bit will rotate with each blade of the bit removing material from the workpiece creating the desired profile. Other cutting tools, such as shapers, provide a similar effect with only the connection between the cutter bit and tool varying.
As woodworking becomes increasingly popular in the hobby market, and competition increases in the industrial market, a significant number of cutter bits, each presenting a corresponding profile, have been developed. Additionally, as the size of routers continues to increase, cutter bits having increasingly complicated and larger profiles are being manufactured. Moreover, a number of bits have been introduced which present multiple profiles depending upon which portion of the bit is in contact with the workpiece.
An important problem associated with larger and more complicated cutter bits for use with router motors is heat build-up within the router bit body. Specifically, when a cutter bit is utilized to impart profiles upon a workpiece at high volume, or alternatively when the workpiece is extremely hard, significant heat may build up in the router bit substantially reducing router bit life. While holes drilled through the router body have been used to reduce the weight of the router bit (addressed below) and to reduce heat within the router body to a limited degree, the need exists for an effective method of removing heat from a router bit in an effort to assure that the cutting tool remains at relatively constant temperature during stressful routing operations. The effective removal of heat from the router bit is of primary concern herein.
In addition, when a cutter bit is in use, the router motor is loaded in a variety of ways. As the cutter bit impinges upon the workpiece and material is removed to create the desired profile, the resistance resulting from the cutting action loads the router motor. Additionally, the weight of the cutter bit itself adds significant load to the router motor. While the load that is a result of cutting action may be substantially reduced by assuring that the cutter bit remains sharp, and has correct bevel angles to remove material chips, the second load, resulting from cutter bit weight, may be reduced only by reducing the weight of the cutter bit.
This second load, which results from cutter bit weight, is also of primary concern herein. This load is insignificant when the cutter bit is small, or when the majority of the cutter bit mass is very near the cutter bit axis of rotation. However, for larger, or more complicated profiles such as multi-profile cutter bits, the cutter bit mass can be significant, with a significant portion thereof being positioned substantially away from the axis of rotation of the cutter bit thereby substantially increasing router motor load as a result of centrifugal force.
Additionally, even when a cutter bit is sharp, and appropriately beveled for chip removal, the cutter bit may nonetheless be loaded with material chips substantially increasing forces felt by the router motor and decreasing the effectiveness of the cutter bit. Additionally, when chips remain positioned adjacent the cutter bit, it is difficult for the user to see the cutting operation. The rapid removal of chips from adjacent the cutter bit is also of primary concern herein.
Thus, the need exists for a cutter bit having a body which significantly increases heat transfer to the surrounding atmosphere during operation and which also has a reduced weight. The need further exists for a cutter bit which assists in removing the chips from adjacent the cutting area, and which quickly unloads chips to the surrounding work surface.